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Sediment contaminant surveillance in Milford Haven Waterway

This comprehensive investigation in the Milford Haven Waterway (MHW), Wales, UK, shows impressively, how the commissioning of two LNG plants, among other factors (e.g. dredging of historically contaminated sediments), had a profound negative impact on benthic and avian health.
“The (…) weight of evidence from independent chemistry and biological monitoring in MHW has shown reasonable doubt concerning the predictions that there would be no significant adverse impacts of the LNG projects developed and operated in combination. The scientific evidence tends to agree with
a complaint lodged with the CEC that the AAs performed for recent LNG projects were fragmentary and
incomplete, and in some cases where there was an absence of adequate knowledge, they also failed to
apply the precautionary principle.”
The authors show some shortcomings of the EIA (environmental impact assessment) for the construction of the LNG plants in the MHW and offer recommendations for future EIAs.

Sediment contaminants were monitored in Milford Haven Waterway (MHW) since 1978 (hydrocarbons) and 1982 (metals), with the aim of providing surveillance of environmental quality in one of the UK’s busiest oil and gas ports. This aim is particularly important during and after large-scale investment in liquefied natural gas (LNG) facilities. However, the methods inevitably have changed over the years, compounding the difficulties of coordinating sampling and analytical programmes. After a review by the MHW Environmental Surveillance Group (MHWESG), sediment hydrocarbon chemistry was investigated in detail in 2010. Natural Resources Wales (NRW) contributed their MHW data for 2007 and 2012, collected to assess the condition of the Special Area of Conservation (SAC) designated under the European Union Habitats Directive. Datasets during 2007-2012 have thus been more comparable. The results showed conclusively that a MHW-wide peak in concentrations of sediment polycyclic aromatic hydrocarbons (PAHs), metals and other contaminants occurred in late 2007. This was corroborated by independent annual monitoring at one centrally located station with peaks in early 2008 and 2011. The spatial and temporal patterns of recovery from the 2007 peak, shown by MHW-wide surveys in 2010 and 2012, indicate several probable causes of contaminant trends, as follows: atmospheric deposition, catchment runoff, sediment resuspension from dredging, and construction of two LNG terminals and a power station. Adverse biological effects predictable in 2007 using international sediment quality guidelines were independently tested by data from monitoring schemes of more than a decade duration in MHW (starfish, limpets) and in the wider SAC (grey seals). Although not proving cause and effect, many of these potential biological receptors showed a simultaneous negative response to the elevated 2007 contamination following intense dredging activity in 2006. Wetland bird counts were typically at a peak in the winter of 2005-2006 previous to peak dredging. In the following winter 2006-2007, shelduck in the Pembroke River showed their lowest winter count, and spring 2007 was the largest ever drop in numbers of shelduck broods across MHW between successive breeding seasons. Wigeon counts in the Pembroke River were low in 2006-2007 and in late 2012 after further dredging nearby. These results are strongly supported by PAH data reported previously from invertebrate bioaccumulation studies in MHW 2007-2010, themselves closely reflecting sediment trends for PAHs in the Pembroke River and Angle Bay.

Little DI, Bullimore B, Galperin Y, Langston WJ
Sediment contaminant surveillance in Milford Haven Waterway
Environ Monit Assess. 2016 Jan;188(1):34. doi: 10.1007/s10661-015-5017-1. Epub 2015 Dec 16.


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